Generally, the instrument boards positioned on the dashboard of the automotive vehicles comprise the displays of several apparatuses, capable of measuring the value of physical quantities concerning the drive of the same vehicle, such as the tachometer, the odometer, and so forth, and a certain number of pilot lamps, which display the operating status of determined pieces of equipment, or critical conditions of physical quantities concerning the drive of the vehicle.
When the instrument board of an automotive vehicle is designed, a thorough investigation into the layout, the dimensions, the types of displays to be adopted is required, in order to find out the best solution for realizing and correctly positioning the various displays within the visual field of the driver and enable this Latter to find out the information with rapidity and precision, without distracting his attention from the road, and from the traffic conditions.
This general criterion is particularly valid for the pilot lamps, because all the operating faults which occur during the vehicle running considerably worry the driver, whose attention, if he finds difficulties in correctly identifying the site of the fault, is distracted from the drive.
Due to this reason, the present trend is to concentrate all of the optical pilot lamps in a particular area of the instrument board, in such a way that they are in front of the driver instead of being partly installed on the instrument board, and partly on a separate panel mounted on the dashboard.
Furthermore, in several cases the solution is adopted of camouflaging the graphic symbols relevant to the optical pilot lamps, so that they are not normally visible, and become visible only when so needed: either when their efficiency is tested, or when they light up in order to display the operating status of a device, critical conditions, faults, so that the driver's attention is surely called to them exactly when the situation so requires.
Usually, a group of optical pilot lamps are directly connected with the respective sensors, while a second group of pilot lamps are operatively connected with the respective sensors through a central control unit.
The central control unit verifies the functionality of the pilot lamps belonging to the second group, by turning them on, when the switchgear driven by the starting-up key is turned on, before the engine is started up. Subsequently during the running of the vehicle, only in case particular operating statuses, critical conditions, or faults, of the devices, occur, the pilot lamps belonging to the first group are directly turned on by the respective sensors, while those
belonging to the second group are turned on by the central control unit.